1. Field of the Invention
This invention relates in general to computer peripheral devices and more particularly to synchronizing an audio cassette played on a standard (unmodified) tape recorder to a computer controlled monitor.
2. Description of the Prior Art
Interactive computer programs where a display is shown on a monitor are often used for educational and training purposes. Instructional capabilities are accelerated when these programs are interfaced with an audio track. Student or trainee interest as well as the rate of receiving and retaining information is increased when the senses of both sound and sight are used. The interfacing of a computer program and an audio track requires careful synchronization and currently takes at least five different forms which will now be addressed.
One form concerns a video cassette or disc which stores both visual and audio information. No synchronization is necessary because the same medium is used. Disadvantages are that video equipment is sophisticated and expensive.
A second approach utilizes the same audio cassette to store the program for controlling the computer as well as the audio track. Again, no synchronization is necessary as the same tape controls the monitor and the audio track. The drawbacks with this approach are that the computer must be designed to facilitate this form of tape storage. Most computers now use disc rather than tape drive because the disc is faster to load and less prone to error.
A third form concerns a computer program controlling a speech synthesizer which uses digitally encoded speech. These synthesizers are expensive and natural sounding digitally encoded speech requires large memory capacity.
A fourth approach uses an audio cassette in a standard tape recorder operating in cooperation with a computer monitor under separate program control. As the tape plays, the computer generates a display on the monitor. After passage of a set time interval equal to the length of the audio segment, the computer turns the tape recorder off. It is difficult to keep the audio and visual sequenced in this approach since everything relies on precise timing. Small irregularities in the tape drive can cause the audio and visual to go further out of synchronization as time passes.
A fifth method uses an audio cassette in a tape recorder controlled by an internal microcomputer which determines exact position by counting the revolutions of both tape spindles. This microcomputer can communicate with the computer interfaced with the monitor and control the spindle drive motors to play specific tape segments in cooperation with the monitor display. This method's drawback is that a specially designed tape recorder is required.